Filter



FIG. 1 is a back view of a filter showing the new design;

FIG. 2 is a front view thereof;

FIG. 3 is a right side view thereof;

FIG. 4 is a left side view thereof;

FIG. 5 is a bottom view thereof;

FIG. 6 is a top view thereof; and,

FIG. 7 is a section view in a direction of 7-7 in FIG. 1. 

CLAIM The ornamental design for a filter, as shown and described. 